The present invention relates to a gas insulated electric apparatus, in which a high voltage conductor is disposed in a sealed vessel filled with insulating gas.
In general, this kind of gas insulated electric apparatus can be constructed in a small size owing to the excellent insulating characteristics of insulating gas, as shows by a gas insulated circuit breaker, a gas insulated switchgear, a gas insulated thyristor valve, a gas insulated voltage transformer, etc. However, it is known that, if foreign metallic matter enters the sealed vessel for some reason, the insulation strength thereof is lowered to a fraction of the initial value.
For example, in a gas insulated electric apparatus disclosed in JP-A-63-124716, it is proposed to store insulating liquid at the bottom of a sealed vessel and to excite an ultrasonic vibrator when insulation abnormalities such as partial discharge, etc. are produced, to give rise to mist (liquid particles of several .mu.m to several tens of .mu.m) of the insulating liquid in order to prevent lowering of insulation strength to suppress the partial discharge.
As described above, in a prior art gas insulated electric apparatus, since lowering of insulation strength is prevented by giving rise to mist of insulating liquids when insulation abnormalities are produced, an insulating liquid storing portion is formed at the lower portion of a sealed vessel. For this reason, in a normal state, the sealed vessel is filled with vapor of the insulating vapor. If a circuit breaker or a disconnecting switch or an earthing switch is operated and an arc is generated in this state, the vapor is decomposed by the arc, and carbon dissociated at this time adheres to the high voltage conductor or insulator, which lowers the insulation strength.